In one class of liquid pumps, a pump body defines a plunger bore within which a plunger reciprocates with each pumping stroke of the device. In order to prevent the plunger from sticking or seizing, a lubricant, such as lubricating oil, must often be employed. In some cases, such as heavy diesel fuel injection pumps, the lubricant itself can sometimes be a source of plungers sticking and seizures due to the formation of precipitates where the lubricating oil comes in contact with the heavy diesel fuel. One such precipitate includes the build-up of calcium carbonate in a plunger bore where heavy diesel fuel has migrated up the side of the plunger into contact with the lubricating oil.
The present invention is directed to overcoming these and other problems associated with the formation of precipitates in lubricated pumps, especially heavy diesel fuel injection pumps.